we talked to co-authors gretchen morgenson, a pulitzer prize winning reporter, and finance analyst joshua rosner outside fannie's headquarters. so the main culprit of your story is fannie mae, right behind you there. why fannie mae? >> it was a primary mover, a first mover in the process to relaxed lending standards, to go downhill into the sort of sub- prime morass that really got us into trouble. and it was able to wrap itself in the american flag of homeownership and capitalize on its great and lucrative government subsidy. >> reporter: how does the government subsidy work? i mean, it isn't the government actually giving money to fannie mae, is it? >> fannie and freddie were given a lower... a lower borrowing rate in the markets by investors who always assumed that they were government-guaranteed. >> reporter: lower borrowing rates because those investors who lent fannie money to buy mortgages believed, if it couldn't pay them back, the government would. and in fact, the government did after fannie's failure in 2008. those lower rates amounted to a $6 billion subsidy, say the authors,